Hi, there! I want to extract all the occurrence of the string starting with the message whose name is "MSG_ID_CELL_INFO_PRINT", and the string starting with the end message name "MSG_ID_CELL_CAMP_REQ". And I also want to compare the "cellid" value of the "MSG_ID_CELL_INFO_PRINT" which is closest to the "MSG_ID_CELL_CAMP_REQ", i.e., the line whose sn=11 vs the line whose sn=15 and sn=24 vs sn=25. If the "cellid" is different, then save all the "MSG_ID_CELL_INFO_PRINT" (or maybe five instances, not all) before the "MSG_ID_CELL_CAMP_REQ" including the "MSG_ID_CELL_CAMP_REQ" into another file. Here is the example data:

MSG_ID_CELL_INFO_PRINT sn=1 cellid=2; 
MSG_ID_CAMP_RSP sn=2 cellid=2; 
MSG_ID_CELL_INFO_PRINT sn=3 cellid=5;
MSG_ID_CELL_INFO_PRINT sn=5 cellid=2;
MSG_ID_CAMP_RSP sn=6 cellid=4; 
MSG_ID_CAMP_RSP sn=8 cellid=2;  
MSG_ID_CELL_INFO_PRINT sn=10 cellid=2; 
MSG_ID_CELL_INFO_PRINT sn=11 cellid=5; 
MSG_ID_CAMP_RSP sn=12 cellid=2; 
MSG_ID_CAMP_RSP sn=14 cellid=3; 
MSG_ID_CELL_CAMP_REQ sn=15 cellid=2; 
MSG_ID_CELL_INFO_PRINT sn=16 cellid=2; 
MSG_ID_CELL_INFO_PRINT sn=17 cellid=2; 
MSG_ID_CELL_INFO_PRINT sn=18 cellid=2; 
MSG_ID_CAMP_RSP sn=19 cellid=2; 
MSG_ID_CELL_INFO_PRINT sn=20 cellid=5; 
MSG_ID_CELL_INFO_PRINT sn=21 cellid=2;
MSG_ID_CAMP_RSP sn=22 cellid=4; 
MSG_ID_CAMP_RSP sn=23 cellid=2;  
MSG_ID_CELL_INFO_PRINT sn=24 cellid=2;  
MSG_ID_CELL_CAMP_REQ sn=25 cellid=2;
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The expected results are: since the "cellid" of "MSG_ID_CELL_INFO_PRINT sn=11 cellid=5;" and "MSG_ID_CELL_CAMP_REQ sn=15 cellid=2;" is different, this information block what I want;

MSG_ID_CELL_INFO_PRINT sn=1 cellid=2; 
MSG_ID_CAMP_RSP sn=2 cellid=2; 
MSG_ID_CELL_INFO_PRINT sn=3 cellid=5;
MSG_ID_CELL_INFO_PRINT sn=5 cellid=2;
MSG_ID_CAMP_RSP sn=6 cellid=4; 
MSG_ID_CAMP_RSP sn=8 cellid=2;  
MSG_ID_CELL_INFO_PRINT sn=10 cellid=2; 
MSG_ID_CELL_INFO_PRINT sn=11 cellid=5; 
MSG_ID_CAMP_RSP sn=12 cellid=2; 
MSG_ID_CAMP_RSP sn=14 cellid=3; 
MSG_ID_CELL_CAMP_REQ sn=15 cellid=2;
[download]

And the "cellid" of "MSG_ID_CELL_INFO_PRINT sn=24 cellid=2;"and "MSG_ID_CELL_CAMP_REQ sn=25 cellid=2;" is same, so this information block is not what I want

MSG_ID_CELL_INFO_PRINT sn=16 cellid=2; 
MSG_ID_CELL_INFO_PRINT sn=17 cellid=2; 
MSG_ID_CELL_INFO_PRINT sn=18 cellid=2; 
MSG_ID_CAMP_RSP sn=19 cellid=2; 
MSG_ID_CELL_INFO_PRINT sn=20 cellid=5; 
MSG_ID_CELL_INFO_PRINT sn=21 cellid=2;
MSG_ID_CAMP_RSP sn=22 cellid=4; 
MSG_ID_CAMP_RSP sn=23 cellid=2;  
MSG_ID_CELL_INFO_PRINT sn=24 cellid=2;  
MSG_ID_CELL_CAMP_REQ sn=25 cellid=2;
[download]

This is my code, I can not figure out how to solve the "nearest compare".

my $str = shift; #the data showed in the above
my $beg = "MSG_ID_CELL_INFO_PRINT";
my $end = "MSG_ID_CELL_CAMP_REQ";
my $key1 = "cellid=";
my $key2 = ";";
while ($str =~ m/$beg.*?$key1(\d+)(.*?)$end(.*?)$key1(\d+)/g) {
 my $info_cell = $2;
 my $camp_cell = $4;
 if ($info_cell ne $camp_cell) {
  my $cell_info = $beg.$1.$key1.$2.$end;
  while ($cell_info =~ m/$beg(.*?)$key2/g) {
  my $print_info = $1;
  print FILEOUT "$beg.$print_info";
  }
 }
}
[download]

The problems of the code are that: first, it compare the first occurrence of the "MSG_ID_CELL_INFO_PRINT" with the "MSG_ID_CELL_CAMP_REQ", for example, sn=1 vs sn=15, which should be sn=11 vs sn=15; Second, once the number of compared value increase, it will be troubled. Also, I can not put the content of the message "MSG_ID_CELL_CAMP_REQ" into file. Any suggestions will be helpful, Thanks!